A biologist at the University of Alberta says this fish, caught in northern Alberta in August, does not have two mouths as originally believed. (Courtesy of Ling Wang)

The unusual-looking goldeye fish caught on Lake Athabasca in northern Alberta last summer did not have two mouths as was initially reported, a biology professor from the University of Alberta said Thursday.

Joe Nelson examined the fish, which first came to public attention during a water conference in Fort Chipewyan in August. Residents of the community took pictures of the fish after it was caught.

"It's immediately obvious that it's just a tongue that's been deflected down through the jaws, and this is something that can happen when the ligaments contract on a goldeye when it dies," he said. "It's a known phenomenon, although not usually seen."

The goldeye's tongue has teeth on it. When the fish in question died, the tongue fell through the soft tissue under the chin creating what appeared to be a second mouth.

The actual fish was frozen and sent to Edmonton for Nelson to examine late last summer, and he was able to quickly confirm that it didn't have two mouths.

"So it certainly looked odd, but no, it's certainly not a mutation — nothing that would indicate a deformed fish," Nelson said.

"It's just a natural occurrence on death."

Pictures of the fish spread around the world. At the time, people thought the apparent deformity was an indication of how oilsands development was affecting Alberta wildlife.

Reports of what Nelson determined only surfaced in the media this week.

The fish is now part of the research collection at the University of Alberta.